pythonlen函数和len方法_为什么Python代码使用len（）函数而不是length方法？

于 2020-11-23 14:49:35 发布 · 170 阅读

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本文探讨了Python中确定字符串长度的方法。作者最初误认为len()不是字符串对象的方法，随后意识到字符串对象确实拥有__len__()方法。文章进一步解释了Python中使用内置len()函数的原理及其与对象导向编程的关系。

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I know that python has a len() function that is used to determine the size of a string, but I was wondering why it's not a method of the string object.

Update

Ok, I realized I was embarrassingly mistaken. __len__() is actually a method of a string object. It just seems weird to see object oriented code in Python using the len function on string objects. Furthermore, it's also weird to see __len__ as the name instead of just len.

解决方案

Strings do have a length method: __len__()

The protocol in Python is to implement this method on objects which have a length and use the built-in len() function, which calls it for you, similar to the way you would implement __iter__() and use the built-in iter() function (or have the method called behind the scenes for you) on objects which are iterable.

Here's a good read on the subject of protocols in Python: Python and the Principle of Least Astonishment